There has been an ongoing loss of life in tragic accidents on offshore drilling platforms partly due to the inadequacy of evacuation systems to remove personnel from platform in emergency situations. For example, it has been reported that evacuation systems have to-date had a failure rate in the order of 86%. This has led to ongoing efforts to improve evacuation systems.
One such system developed by the present applicant is based on an arrangement in which an elongated deployment arm is mounted at the side of a platform with the totally enclosed motor propelled survival craft (TEMPSC) supported at the end of the deployment arm. In an emergency situation the TEMPSC is loaded and the deployment arm pivoted down to the surface of the sea, controlled by a winch and cable.
An important aspect of the system is the winch. The winch must fulfil a number of stringent design criteria. These include the fundamental requirement that the winch be capable of deploying the TEMPSC in a situation where there is an electrical power outage on the platform. The launch must obviously be at an acceptable low rate of speed and so a significant amount of energy must be dissipated by the winch. Furthermore, the winch must then be capable of recovering the TEMPSC and restoring it to the ready position. This last function is of particular importance for test purposes.
In addition to the operational requirements, the winch must be capable of operating in a hostile environment and must remain in top operating condition with minimum maintenance.
It is against this background that the present invention arises.